1. Field of the Invention
The present invention relates to prevention of water vapor condensation in a television camera apparatus.
2. Description of Related Art
In order to maintain favorable performance of image-pickup elements such as image-pickup tubes and solid-state image-pickup elements and to lengthen their lives, temperature control has conventionally been performed so that temperatures of the target surfaces of the image-pickup elements are kept substantially constant.
However, when image-pickup elements are cooled in a high-temperature and high-humidity atmosphere, water vapor is condensed into water on the surfaces of the image-pickup elements in some cases. If image shooting is performed with a television camera in such a state, there arises a problem that blurred images will be produced. Therefore, conventionally, in order to prevent water vapor condensation on the surfaces of image-pickup elements, the humidity in the environment in which the television camera is used is limited, temperature-decreases of the surfaces of the image-pickup elements are limited, or sealing tightness in the optical system (prism) housing to which the image-pickup elements are attached is improved. Moreover, the inside air is dried by a dehumidifying agent or the like. Thus, water vapor condensation due to cooling of the surfaces of the image-pickup elements has been prevented.
Conventionally, the environment in which the apparatus is used is restricted to prevent water vapor condensation on the surfaces of the image-pickup elements, and consequently, the mobility of the apparatus is deteriorated in some cases. In the case of a structure in which an increase in humidity is suppressed by increasing sealing tightness of the prism housing, it is necessary to raise the accuracy in machining of component parts, thus increasing the manufacturing cost of the component parts. Further, the maintenance of the apparatus is difficult, and the apparatus is not fit for long-term repeated use.